EP0690173A1 - Reinforced poured asphalt - Google Patents

Abstract

The asphalt consists of a bitumen binder, filler and sand in the normal proportions for a primary sealing coating, mixed at a temperature of 200 to 250 deg.C. The mixture contains between 0.1 to 1.0 per cent, and preferably 0.2 per cent by weight in relation to the binder of short glass fibres in bundles which are softened at the mixing temperature so that the fibres are dispersed freely. The glass fibres are between 12 and 50 mm, and preferably about 25 mm, long, with a diameter of some 24 microns, and they can be introduced directly into the mixing trough of a mixer/transporter truck. <IMAGE>

Description

The present invention relates to formulations of poured and reinforced asphalt by means of a filler making it possible to improve certain mechanical properties, in particular at low temperature. The invention further covers applications of said formulations in the form of coatings.

We know that mastic asphalts are made of hot mixtures of bitumen, filler, sand and gravel, in proportions that characterize the application for which they are intended, for example building waterproofing, waterproofing of parking lots or decks , or simply road surface layer. The mastic asphalts are implemented by hot pouring and usually without any reinforcement.

However, an additional mechanical performance has been sought-by the use of reinforcements, such as a glass fabric, a glass veil or a glass grid, or even a metallic mesh, such a known technique having been implemented by various users. However, the reinforcement effect thus obtained is exerted substantially in a single plane, preventing the obtaining of homogeneous properties which would in particular be required in the case of coatings subjected to mechanical stresses at low temperatures. Furthermore, fillers of glass fibers have been incorporated into asphalt, but only for the purpose of strengthening the retention between them of gravel forming the essential mass of said asphalt, which is a material of formulation very different from that of poured asphalt and which is implemented by compaction instead of being implemented by pouring like poured asphalts.

The present invention therefore aims to remedy the above drawbacks, by providing poured asphalt formulations comprising a reinforcement producing its effects in almost all directions instead of producing them only in a direction parallel to the coating, producing its effects throughout the mass of the coating instead of producing them only in a single plane and in particular giving asphalts better resistance to hot punching without the need for incorporation a hardener, while improving the elasticity maintenance characteristics at low temperatures, particularly suitable for producing waterproof coatings.

According to the invention, a poured asphalt formulation, comprising a binder consisting of bitumen, filler, sand and gravel, obtained by hot mixing between about 200 and 250 ° C., contains from 0.1 to 2%. by weight with respect to the binder of short glass fibers, the size of which is capable of exhibiting softening at the mixing temperatures of the binder, so as to release the constituent fibers of the fibers.

Advantageously, the glass fibers have a length of approximately 25 mm for a diameter of approximately 24 microns and consist of at least 10 elementary threads.

• la figure 1 représente un graphique traction-rupture comparatif de quatre formulations d'asphalte coulé ;
• la figure 2 représente un graphique traction-rupture comparatif de deux formulations dont l'indentation est différente ;
• la figure 3 représente un graphique comparatif de l'indentation en fonction de la teneur en bitume 40/50 dans le liant total de formulations selon l'invention ; et
• la figure 4 représente un graphique comparatif de l'indice de maniabilité en fonction de la teneur en bitume selon la figure 3.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings in which:

• FIG. 1 represents a comparative tensile-breaking graph of four formulations of poured asphalt;
• FIG. 2 represents a comparative tensile-breaking graph of two formulations whose indentation is different;
• FIG. 3 represents a comparative graph of the indentation as a function of the bitumen content 40/50 in the total binder of formulations according to the invention; and
• FIG. 4 represents a comparative graph of the handling index as a function of the bitumen content according to FIG. 3.

The Applicant has determined in the course of its work that the reinforcing effect acting in almost all directions and exercising throughout the mass of the coating is obtained by means of the elementary wires of a load of short glass fibers , that is to say of a length between 12 and 50 mm, preferably 25 mm, and each composed of at least 10 elementary son which ensure the desired homogeneity effect. However, the release of these elementary threads within the binder at its mixing temperature of between 200 and 250 ° C. requires a size that softens in this temperature range, which is not the case for example for glass fibers intended thermal insulation. Given these imperatives, including those influencing the cost price and the ease of implementation, the Applicant has defined a type of fiber which is close to certain textile fibers, an example of which is those used in the trade under the name VETROTEX, in particular the quality known as P 103/25 which corresponds appreciably to the characteristics which the Applicant considers necessary for obtaining the desired properties.

The Applicant has found that the addition of this type of glass fiber in the mixture of poured asphalt gives the finished product a surprising improvement in the mechanical characteristics, in proportions of between 0.1% and 2% of the total weight of the mixture. , the proportion of 0.2% being preferred, because it confers mechanical advantages without reducing the workability of the product to be used.

With equal indentation, the cold traction characteristics are markedly improved, as is apparent from the graph in FIG. 1 where the elongation has been plotted on the abscissa in tenths of the elongation percentage relative to the initial length and on the ordinate the tensile force in hundreds of Newtons. In a manner known per se, the test is carried out at a constant tensile speed of 1mm / min. According to the graph in fig. 1, the tensile-rupture curves were obtained at -10 ° C for a sealing formulation with or without fibers and in two cases of indentation, namely: curves 1 and 2 without fibers, respective indentations IdA 10 and 25, curves 3 and 4 with 0.2% fiber, same respective indentations. The formulations with fibers have interesting elongation levels (3, 4) while the formulations without fiber give brittle fractures (1, 2).

It should also be noted that, with an equal dosage of bitumen, the addition of fibers, even in small quantities, reduces the indentation, that is to say improves the puncture resistance of the finished product. Thus, the graph in FIG. 2, whose coordinate axes have the same units as in FIG. 1, shows that for a very small quantity of fibers of 0.1% the tensile-breaking diagrams are roughly equivalent whereas the indentation is profoundly modified by the presence of the fibers: 51 without fibers (curve 5) and only 38 with fibers (curve 6), these tests having been carried out at -10 ° C.

The addition of short glass fibers therefore makes it possible, by determining the suitable proportion having regard to the use for which the finished product is intended, to adjust the characteristics in cold traction and the characteristics in indentation at positive temperatures. For parking surfaces in particular, it is desirable to have good tensile strength when cold and appreciable elongation before breaking, to avoid cold breakdown. It is also desirable, at positive temperatures, to have good puncture resistance to avoid deep marking of tires on parked vehicles.

Usually, the punching resistance for positive temperatures is improved by adding a bitumen called "hardening bitumen" in addition to the 40/50 bitumen. The fraction of hardening bitumen, grade 105/6, varies depending on the application, from 10% to 35% of the total weight of the binder. The cost of this hardening bitumen is almost five times the usual 40/50 bitumen. The total cost of the binder is therefore multiplied by 1.4 or 2.4 depending on the application, which must be agreed for parking surfaces that do not puncture. In addition, this hardener bitumen has the drawback of stiffening and weakening the finished product when cold, the hardness desired at positive temperatures having, on the other hand, brittleness when cold.

Quite usually, when we do not want to use bitumen 105/6 we use bitumen 20/30 stored in a heating tank, which is introduced into the kneader by pumping in addition to the introduction of bitumen 40/50 . We are therefore obliged to have on the installation the possibility of storing in heating tanks two different bitumens and to bear the costs relating to this bi-storage. The rheological disadvantage is the same as previously, namely that obtaining the desired hardness at positive temperatures has for counterpart a brittleness when cold.

The addition of short glass fibers, in appropriate proportions, makes it possible, on the contrary, to obtain good resistance to punching when hot, while preserving sufficient elasticity when cold and this without using the hardening bitumen: there is an appreciable saving of material, because for a proportion of glass fibers P 103/25 of approximately 0.1% the impact on the finished product is appreciably seven times lower than that which would be due to the presence of approximately 2% of hardener bitumen.

Furthermore, with regard to the manufacturing economy, it should be noted that the hardener bitumen 105/6 is solid at room temperature. It is delivered by metal drums which must be stored, handled, then cut to extract the product which is then cut up to the mass, then weighed before being introduced into kneaders.

With the glass fibers according to the invention, all these operations are eliminated, as are all the costs and drawbacks relating to a possible dual storage of hot bitumens. Indeed, the introduction into the mixture is carried out by directly emptying the number of bags of fibers required in the kneader.

It is also noted that the introduction of the fibers directly into the kneading chute of the kneading machine at the time of loading of the locomixer transport truck is a simple and convenient means. The dispersion of the fibers in the mastic asphalt is very good thanks to the turbulence of the loading operation and it is further improved by the mixing which continues during transport.

To arrive at establishing the best formulations according to the invention, the Applicant has determined the dosages having the desired effects while exhibiting good workability during use.

• courbe 7, correspondant à 16% de liant total et à 0% de fibres ;
• courbe 8, correspondant à 16% de liant total et à 0,2% de fibres ; et,
  par comparaison :
• courbe 9, correspondant à 15% de liant total et à 0% de fibres ;
• courbe 10, correspondant à 14% de liant total et à 0% de fibres.

The graphs in Figures 3 and 4 summarize the results obtained. On these graphs, we have plotted on the abscissa on a linear scale the percentage of bitumen 40/50 in the total binder which may comprise a hardening bitumen 105/6, said total binder representing 14% or 16% by weight of the final product, as will be better explained below. On the graph of FIG. 3, the Wilson W indentation has been plotted on the ordinate on a logarithmic scale and the two min and max values of the usual range have been shown. The following curves were obtained:

• curve 7, corresponding to 16% of total binder and 0% of fibers;
• curve 8, corresponding to 16% of total binder and to 0.2% of fibers; and,
  by comparing :
• curve 9, corresponding to 15% of total binder and to 0% of fibers;
• curve 10, corresponding to 14% of total binder and 0% of fibers.

Curves 7 and 8 are the most interesting to compare: we see that curve 8 indicates a reduced indentation and always located in the usual range 20/80, even when there is no longer any hardening bitumen (bitumen content 40 / 50 equal to 100% of the total binder). It can also be seen that curve 8 indicates very good handling even when there is no longer any hardener (40/50 content equal to 100%). In the latter case the maneuverability is in the vicinity of the maximum of the usual range.

These results demonstrate that the formulations (8) with 16% of total binder and with 0.2% of fibers are efficient and that the hardening bitumen is not necessary to obtain the desired result.

On the graph of FIG. 4, comprising the same units on the abscissa as in FIG. 3, the workability Km obtained using the Bernard-Brunel method has been plotted on the ordinate on a logarithmic scale standardized. The values of the usual min-max range have also been shown. On this graph, the curves 11, 12, 13, 14 correspond respectively to the formulations of the curves 7, 8, 9, 10. It is clear from the two diagrams of FIGS. 3 and 4 that the formulation giving curves 8 and 12, in particular 100% of 40/50 bitumen in the binder, is particularly advantageous.

The formulations according to the invention can be successfully applied for single-layer waterproofing coatings of the sand asphalt type, in sites where the annual difference between the maximum and minimum temperatures is very large. Furthermore, said formulations are particularly useful for producing the first layer of pure asphalt of bi-layer coatings known per se and intended for car parks or engineering structures, it being understood that for these coatings the second layer of gravelled asphalt cannot be armed because, during hot brewing, the impact of the gravel would destroy the glass fibers.

It is understood that the present invention has been described for explanatory purposes but is in no way limitative and that any useful modification may be made to it, in particular in the field of technical equivalences, without going beyond its ambit.

Claims (5)

Reinforced mastic asphalt, of the type comprising bitumen binder, filler and sand in the proportions usually used for mastic asphalts used in the first layer of waterproofing coatings, obtained by hot mixing between approximately 200 and 250 ° C, characterized by the fact that its formulation contains between 0.1 to 1%, preferably 0.2%, by weight relative to the binder, of short glass fibers whose size exhibits softening at mixing temperatures, so that that the protective layer of the fibers is dispersed in the bitumen in order to completely release the constituent yarns of said fibers. Poured asphalt according to claim 1, characterized in that the glass fibers have a length of between 12 and 50 mm, preferably about 25 mm, for a diameter of about 24 microns and that they consist of at least 10 elementary children. Poured asphalt according to one of claims 1 or 2, characterized in that the glass fibers are introduced directly into the kneading chute for the mixer when loading the transport mixer truck. Application of a reinforced mastic asphalt according to any one of claims 1 to 3 to the production of a single-layer waterproofing coating of the sand asphalt type. Application of a reinforced mastic asphalt according to any one of Claims 1 to 3 to the production of the first layer of pure asphalt with a two-layer waterproofing coating.

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